Hydraulic brake mechanism



R. J. KLIMKIEWICZ 2,377,699

June 5, 1945.

HYDRAULIC BRAKE MECH ANISM Filed Sept 30 1943 2 Sheets-Sheet l June 5, 1945.

R. J. KL'IMKIEWICZ HYDRAULIC BRAKE MECHANISM Filed Sept. 30, 1943 2 Sheets-Sheet 2 than the brakes.

:of the booster pedal. i .A, further object is to provide such an appa- Patented June 5, 1945 s PATENTDFFICE HYDRAULIC BRAKE MECHANISM Rudolph J. Klimkiewicz', Newark; N. J assignor, by mesne assignments, to Empire Electric Brake Company, of New Jerscy Newark, N. J., a corporation l i AppIicationIS eptemberIiO,1943, Serial'N0h504A51 8C1aims. 1 (c1. (so-54.5)

This invention relates to hydraulic brake mechanisms, and more particularly to a hydraulic booster brake mechanism for motor vehicles,

I of the type wherein thebooster unit is connected ojthe vehicle master cylinder and to the wheel cylinders by hydraulic lines, whereby the mechanism i renderedoperative byfluid displaced from the master cylinder to increase the hydraulic'pressure in the brake cylinders to apply thebrakes a A number of highly efficient and commercially practicable hydraulic booster brake mechanisms improving the "feel in the brake pedal, by making it; accurately proportional under all. conditions to the degree of brake application;

A' further object is to provide a brake mechanism of this character wherein the substantial use of stampings and the duplication of elements for different parts'of theapparatus combine to a reatly reduce the cost of manufacture of the 1 devicefl H Other objects and advantages of the invention will become apparent during the course of the following description.

have been developedwherein the hydraulic fluid displaced from a vehicle master cylinder is uti- -lized for actuating a booster motor ftodisplace fluid into the brake cylinders toapply the brakes,

the pressure developedby the foot of the operator performing part of the work in applying the patents to Berteli Stelzerj Nos. 2,260,490, 2,260,491 and 2,260,492, granted October 28, 1941.

While devices of the type "referred to have proved to be highly practicable in operation, it is desirable that the cost of manufacturing devices H y practicablemechanisms of l the type referred to are shown, for example, in

In the drawings I have shown one embodiment of the invention. Inthisshowingfl "Figure 1 is a central axial sectional View through the booster unit, parts being broken away and parts being shown in elevation, the

mast-ereylinder and associated elements, and

the wheel cylinders being showndiagrammati-l cally in connection with the booster unit,

Figure 2 is a section taken substantially on line -2 of Figure 1, parts ,being broken awa and parts being shown in elevation, l 1

Figure 3 is anenlarged fragmentary sectional of this character be reduced. It isalso highly desirable to provide a device or this character wherein the valve mechanisms operate to propossible to movevide was rapid a response as ments of the vehicle brake pedal. An important object of the "present invention is to provide a power operated brake mechanism of the generallcharacterreferred to wherein the valve mechanism is of such character as to provide ,an extremely rapid motor to movements of the brake ratuswherein a multiplied movement of the valve parts *takes place fora given displacement of fluid fromthe master cylinder, thus increasing the rapidity of the response of the booster motor to movements of'the brake pedal. '1

A further object is to provide a power-operated booster brakemechanism whereinfsimple,

fluid pressures in the booster-motor, thus reducingthe cost of manufacture ofuthe device while greatlyimproving-the efliciencyofgthe mechanism.

i A further object is to provide such a me'chahim which is extremely sensitive aslto feel? and as to the accuracy of the follow-up operation of the booster motor with respect to the movement of the brake pedal, such accuracy and sensitive response view taken centrally associated element's, v

Figure l is a similar view taken through the through the air valve and fluid is displacedfrom the master cylinder I I through a conduit l4 to a booster unit indicated as a whole by the numerall5, From the booster unit, fluid is displaced through a conduit IE -to the four wheel cylinders of the braking mechanism, all of which are conventional and are 45 economically manufactured poppet valves are employed for controlling indicated by the numeral l1.

-The booster mechanism co'inprises a motor formed of a pair of easing sections I8, and I9 which are preferably stampings from the same dies. Thesestampings are provided with complementary grooves 20 to receive the preferably thickened edge 2| of a flexible diaphragm 22.

, The outer peripheral edges of the casings l8 and F9 are received in'a stamped split clamping ring 23 the ends of which are provided with lugs 24 (Figure 2) through which passes a bolt 25 to clamp the ring 23 in positionand thus secure the numeral I 0 desigpassage 38 communicates with one end of a cylv inder 32 formed in the element 29, such end of the cylinder 32 being designated by the numeral 33 and forming an inlet or primary pressure chamber. At the same end of the cylinder 32, the element 29 is provided with a stop lug 34 for a purpose to be described.

The flange 28 is an integral part of a second cylinder element 35 having a cylinder 36 formed therein with the end 31 of the cylinder forming an outlet or secondary pressure chamber. The cylinder element 35 is provided with a passage 38 communicating with the conduit IS, a union 39 being employed for providing a mechanical leakproof connection between the cylinder element 35 and the conduit IS. The element 35 is also provided with a stop lug 40 identical with the stop lug 34. It will be apparent that the cylinder elements 29 and 35 are identical with each other, thus materially reducing the .cost of producing the two cylinder elements for each booster unit. Likewise, the attaching screws 26 or other fastening elements are identical with each other, and the same is true of the unions 3| and 39.

A stamped steel plate 4| is arranged against the-diaphragm 22 as shown in Figure 1. This plate is provided with a retaining ring 42 preferably welded thereto and having an annular dished portion 43 to receive the enlarged inner peripheral bead 44 of the diaphragm 22 to thus secure the inner peripheral portion of the diaphragm to the plate 4 I.

A piston structure indicated as a whole by the numeral 46 is adapted to be actuated by fluid displaced from the master cylinder and by the differential pressures affecting the pressure responsive unit of the motor comprising the diaphragm 22 and plate 4|. The piston structure 46 comprises a piston body 81 having an opening 48 extending from the left hand end of thebody 41 as viewed in Figure 1 to a point spaced from the other'end of the piston body. The opening or bore 48 communicates through an opening 49 with an axial opening 58 formed in the right hand end of the piston body 41 as viewed in Figure l. A rod 52 (Figures 1 and 2) is mounted in the opening 48 and has a restricted end 53 projecting through the opening 49 and engaging a ball valve 54 the outward movement of which is limited by a stop pin 55. During operation of the mechanism the ball 54 seatsagainst the adjacentend of the opening 49. When the parts are in the off positions shown in Figure 1, however, the

rod extension 53 maintains the ball 54 off its seat to aiford communication between the chambers 33 and 3? for a purpose to be described. The lug 34 (Figure 1) contacts the adjacent end of the rod 52 to move the ball 54 from its seat when the parts approach the oil positions as will become apparent.

The right hand end of the piston structure 41 (Figure 1) is slidable in a bearing sleeve 58 driven into apiston sleeve 59, the right hand end of the sleeve 58 having an annular flange 68 seating against the adjacent end of the sleeve 59. The flange 69 slidably fits in the cylinder 38 to be rates the reduced piston portion 64 from a groove 66 formed in the pistonbody. A bracket indicated as a whole by the numeral 61 is provided with a vertical wall 88 notched as at 69 (Figure 5) toreceive the portion of the piston body defined by the groove 66. Referring to Figure 1, it will be noted. that'the. wall 88 of the bracket element is thinner than the width of the groove 58 and accordingly the piston body is slightly movable toward the right in Figure 1 independently of the bracket wall 68. This slight movement is utilized'fo'r the operation of the valve mechanism to be described.

The bracket element 6'! is provided with spaced vertical side walls 18 and with oppositely extending foot portions H having openings 12 to receive screws 73 (Figure 2) whereby the bracket element maybe secured rigidly to the plate 4|. Accordingly it willbe apparent that the bracket element 51 moves with the pressure responsive unit of the motor. Referring to Figure 1, it will be noted that the bracket Wall 88 engages an extension 14 formed integral with the cylinder element .29. The cylinder element 35 carries a similar extension 15, but thiselementperforms no particular function except for somewhat elongating cylinder 36. As previouslystated, the cylinder elements 29 and 35 are identical for economyin manufacture, and the lug 40 also'performs no function, this element being present solely becauseof the identity of the two cylinder elements;

A spring 18 surrounds the piston body-4'| and has one end seating against the bracket wall '68. The other end of this spring engages a spring seat Tl held against movement by a two-part retaining ring 18 which, in turn, is retained in its groove in the piston body by an under-cut ring 19. The latter ring backs up a suitable packing cup 88 on the adjacent end of the piston structure 41.

The plate 4| of the motor is provided with stamped cylindrical recesses 8| and 82 on diametrically opposite sides of the axis of the motor, and these recesses respectively contain the air control and vacuum control valves. The air control valve is shown in detail in Figure 3 and the vacuum control valve is similarly shown in Figure i. Referring to Figure 3, the numeral 83 designates a sleeve pressed into the recess 8| and having a front wall 84 turned inwardly at its inner peripheral edge as at 85 to form a valve seat. A'valve element BB-is formed of a conicalbody 81 having a closed outer end 88, and the opposite end of the body 81 is formed integral with an outstanding flange 89 against one faceof which is secured in any suitable manner a valve element 90 engageable against the seat 85. The valve element 98 isnormally closed, as will be referred to later.

A goose neck 9| (Figures 2 and3) has one end device 86.

:A rubber or Similar flexible hose 96 has one end clamped as at 91 to the (outer .end of the goose neck :91, and the other end of the hose isclamped as :at 99 toa pipe 99 extending through the motor casing I 9 and preferably welded I thereto. The

- pipe 99 forms the air inlet for the motor, if the motor is operated by vacuum, and is connected to I vided with a flange vI2 'l seatingagainst its asso a source of super-atmospheric pressure if the motor is to be operated by such pressure. It is preferred that the motor be vacuumoperated, in which case the pipe 99 is preferably connected to any suitable type of air cleaner (not shown).

The low pressure or vacuum control device is substantially identical with the valve device just described. Referring toFigure 4, the valve device is indicated by the nun-leral I and comprises a frustro-conical body HH having a closed end-I02. An integraloutstanding flange I02 is carried by the body IIJI and is providedfwith a valve element I 93 engageablewith a seat I04 formed as a ring raised from the bottom of the recess 82 by the internal die used in forming this recess. The valve'element I03 is normally slightly unseated. .A spring M5 is engageable at one endagainst the bottom of the recess 82 and has its other end engaging-the closed end I02. This spring, therefore; tends to unseat the valve element I03, whereas the spring 95 (Figure 3) tends to seat the valve element 90. the bottom of the recess 82 tion between opposite ends of themotorflfi when the valve element I63 is unseated.

A' lever device indicated as a wholeby the numeral III) controls the operation of the two valves described. The lever device comprises a pair of preferably identical stamped lever elemerits III and II2 each of which has an angularly extending portion I I3 extending toward the other lever element. Each such angular exten-- sion'terminates in a foot II I seatinga'gainst the other Ilever elementandsecuredthereto by a bolt I I5. The arrangement referred to spaces the intermediate portionsiof the lever elements -and such portions straddle the reduced portiontd of the piston body 41. Each edge of the central portion of each lever element is provided with a raised portion H6, such raised portions at one side of the lever-device engaging the shoulder I I1 formed at the right hand end of the reduced portion 64 of the piston body 47; while the raised portions H6 at the opposite side of the leverdevice engage the flange 65. The lever element H4 is provided with a laterally extend ingfoot H8 engaging the closed end 88 of the valve body 87. Bee lever element I I 2 is provided i:

with a similar foot I I9 engaging the closed end I02 of the valve body IOIL As previouslystated, the motor I5 is preferably vacuum operatedl in which case the pressure movable unit is vacuum suspended when the valve element I133 is in its normal open position as shown in Figure 4. The motor casing I9 car ries a pipe I extending therethrough and preferably welded thereto; and when the motor is vacuum operated the pipe I20 is connected to a} suitablesource of vacuum, such as the intake manifold of a motor vehicle engine. If the motor is to be operated by super-atmospheric pressure, the pipe I20 is preierably provided with a suitable air cleaner (not shown) and directly communicatesiwith the atmosphere.

Referring to F'igure 2, it' will be noted that each lever element I I0 and III carries a pin I operable in a slot I26 formed in the adjacent, bracket wall 79, Each of these pins maybeprm Openings I96 in afiord communica- I toward the right as viewed in Figure 1.

ciated lever, -and the innerend of the pin may be riveted to the lever. This arrangement retains the leverdevice H0 in its proper-position, as will become apparent.

While the return springs of the wheel cylinders may be depended upon to returnthe parts to normal position, it is preferred that the motor I5 be provided with a return spring I28, as shown in t Figure 1.

I The operation of the apparatus is as follows:-

The parts normally occupy the positions shown in thedrawings, as stated above. When thetbperator desires to apply the brakes; he will depress the brake pedal ter cylinder II through pipe I I. The hydraulic fluid flows into the chamber 33, thence through the passage 48 around the rod 52 which is square in crosssecti'on; as shown in Figure 2. From the passage 48, fluid flows into the secondary cham ber 31 and thence through pipe line It for distribution to thebrake cylinders Il. Thus it will be apparent that initial displacement of fluicl from' the master cylinder operates to at least partially take up the slack between the brake shoes and drumsprior to energization of themotor I5. I I If the flow of fluid takes placein the manner described until all play tween thebrake shoes and drums, resistance to further movement of the shoes will result in an immediate increase in pressure throughout the fluid lines from themaster cylinder to the brake cylinders. This increased pressure willloe the same in the chambers33 and 37 (Figure 1) but the area of the :piston in the chamber 33 will be greater than the area of the end of the piston body Ill?exposed-to pressure in the chamber 31. Accordingly the piston body 4'! will be subjected to difierentia l fluid pressures which will move it The playbetweeh the left wall-of the groove 66 (Figure 1) and the bracket wall BB permits the piston body 41 to move toward the right independently of the sleeve 59 and the other elements- I of the pressure responsive unit of the motor I5.

a movement of thevalve lever will move the valve Such movement of the piston body 4'! will cause the flange 65 to push toward the right (Figure 1) against the central portion of the:lever device H0; T'he spring 95 is somewhat stronger than thespring I65 of the vacuum valve, and movement imparted to the center of the lever device II II will therefore take place with the lever device fulcruming at the point of contact of the foot I I8 against theend wall 88 of the valve body 87. Thus the opposite end of the lever device will move toward the right to move the valve body H19 in the same direction. Since the distance between the contact points of the lever de I vice HQ with the valve bodies 8% and I99 is twice distance between the point of engagement of the flange (i5 with the lever device and the the point of contact of the foot H8 with the valve body 86, it will be obvious that the described body I90 a distance twice as ment of the piston body 41. y I Avery short distance of movement of the piston body 47 accordinglynis necessary to seat the great as the movevalve element I93 (Figure 4e) and thus close communication betweenthe two ends of themotor I5. Further movement ofthe piston body 41 will take place with the lever device llll fulcruming at its lower end in Figure l I with the 13 to displace fluid from themashas been taken up beupper end of the lever device moving twice the distance of movement of the piston body 41. This movement unseats the valve element 90 (Figure 4) and air will flow through pipe 99, flexible hose 96 and goose neck 9|, around the air valve device and into the motor casing I8. The motor casing l9 remains in fixed communication with the source of vacuum through pipe 120, and accordingly difierential pressures will be established in the motor to move the pressure movable unit of the motor toward the right as viewed in Figure 1. r

The operation referred to causes the sleeve 59 to move toward the right to displace fluid from the pressure chamber 31 into the brake cylinders. At the same time it will be appreciated that movement of the piston body 41 toward the right in Figure 1 will have moved the ball 54 and the adjacent end of the opening 49 relatively toward each other, thus seating the ball and cuting off. communication between the primary chamber 33 and the secondary chamber 31. Thus a braking pressure will be built up in the chamber 3'1 which will be the result of manual displacement of fluid by movement of piston body 41 toward the right, and displacement of fluid by the power actuation of the sleeve 59 and flange 60. Thus it.will be apparent that a portion of the work involved in generating the braking pressure in the chamber 31, and accordingly in the Wheel cylinders, will be performed by the operator by manual actuation of the pedal l3,

the remaining work being performed by the fluid pressure motor E5. The proportionate work performed by the operator and by the motor maybe determined in accordance with the relative areas of the piston element which displace fluidv from the chamber 31, as will be obvious. It also will be apparent that any pressure in the chamber 31 will react upon the foot of the operator by opposing manual movement of the piston body 41 to a degree proportional to the braking pressure, thus providing the pedal 13 with highly accurate feel.

operation of the brake pedal will result in corresponding movement of the piston body 41. The cross sectional area of the primary chamber 33 being equal to the cross-sectional areas of the master cylinder, the piston body 41 will always move the same distance as the piston 12. Such movement of the piston body 41 will be transmitted to the lever device H at the center thereof and the lever device will fulcrum at either end to effecta movement of the opposite end of the lever device which will be twice the movement'of the piston body 41 and the master cylinder piston I 2. Assuming that a continuous movement of the pedal !3 takes place up to the desired maximum application of the brakes, the continued application of force against the center of the lever device H!) by the piston body 41 will cause the air valve element 90 to remain off its seat to continuously feed air into the motor casing '18.

When the movement of the pedal 13 is arrested, movement of the piston body 41 will immediately cease and the pressure movable unit of the motor will continue to move, but only to the extent of an extremely small fraction of an inch. Such movement will be sufiicient to permit the air valve 90 to close. Any tendency for the pressure movable unit of the motor to overrun to an appreciable extent will be prevented by the fact that upon the closing of the air valve,'any slight addie tional movement of the pressure movableunit of the motor will tend .to move the valve seat I04 (Figure 4) away from the valve element I03 to thus unseat this valve and establish restricted communication between the chambers of the motor casing. This will effect a sufficient exhaustion of air from the motor casing 18 into the motor casing [9 to arrest movement of the motor parts.

When the brake is to be released,- the operator will release the pedal 13 to retract the piston 12, whereupon pressure in the brake lines tothe wheel cylinders and in the chamber 31 will force the pressure-generating piston elements of the device toward the left as viewed in Figure 1. Pressure being first released in the master cylinder, the piston body 41 will be freely movable and will move in advance of the pressure movable unit of the motor, and such advance movement of the piston body 41 will reverse the previously described operation of the valve except that the air valve (Figure 3) ordinarily is closed after full brake application has occurred, in which case initial movement of the piston body 41 to the left will cause the shoulder H1 to engage the center points of the lever device I Ill toswing the lower end of the lever device toward the left in Figure 1 to unseat the vacuum valve 03. The air valve 90 having been closed, the opening of the vacuum valve 103 -will equalize pressures in the two motor casings, and the reciprocating parts will be moved back to their normal positions by the return springs in the brake cylinders and by the motor return spring 128. As the piston body 41 approaches normal position, the lug 34 will engage the rod 52 and hold it stationary .to thus unseat the ball valve 54 as the piston body 41 partakes of its last increment of rnovement to its off position.

It will be apparent, of course, that ment of the pins I25 (Figure 2') in the slots I26 of the brackets 61 prevents displacement of the lever devic H0 endwise thereof. Particular at tention is invited to the fact that the present device is highly advantageous for two distinct reasons because of the inclusion of the lever device and the poppet valves operated thereby. In the first place, the arrangement shown is substantially more economical to manufacture than sliding internal valves, it requiring relatively expensive machining to accurately fit the sliding valves to provide accuracy and stability in operation without undue leakage. The valve devices shown are made of simple stampings and the two valve bodies 86 and are identical with each other and produced by the same dies. In the second place, the arrangement shown is highly advantageous for the reason that any movement of either valve takes place through twice the distance and at twice the speed of the movement of the piston body 41 which results in such valve movement. It will be readily appreciated that the leverage increase provided by the mechanism shown and described results in a more rapid response of the motor to operation of the master cylinderthan can possibly be obtained by internal valves which move a distance equal to movement of the piston of the master cylinder. The use of poppet valves eliminates any leakage, such as occurs with sliding valves, and the resulting construction is such that an extremely accurate and instantaneous follow-up of the motor with respect to operation of the brake pedal takes place. i

- The leverage referred to permits the clearance between the bracket wall 68 and the left hand wall 1 the engagedifierent cylinder element 35 movable in saidhigh oi the groove" 66-: to be madeextremely small. In the event of a 'iallureoi power'in the motor the play referredto will be taken upby manual displacementof the piston structure "t'lwand the bracket element 61 will be manually operated to transmit manual movement through the 'plate 4t to the sleeve 46 The two pressure-creating 2 piston elements will thereupon be operated: man-- uallyas a single unit and th lost motion necessary toube taken. up for the manual. operation of the brakes is-negligiblet l v 1 As previouslypointed out the present structure is capableof highly economical manutacture inasmuch as most of the parts are simpledie casting's or stampings and thereis: a substantial. duplication. of elements" to materially reduce the number of dies required to produce the'appa'ratus. For example,..the cylinder elements 29 and 35 may be: identical diecastings, the: motor casings [8 and :l'a' mayibe stamped iromlthe' same dies; the

lever elements I 10' and Hi may be similarly iden tically stamped; and the same istrue :of the valve bodies) and. Hill. The' present device, therefore, possesses all of the advantages of prior devicestoperating on the same principle andis highly advantageous over such prior devices because-of economy in manufacture, and because of its instantaneous and accurate operation,

The apparatus: has been. particularly illustrated in its applicationltd at four-wheelcbrake system of conventional type. With such an arrangement, the displacementof liquid: from the pressure chamber 31' isalways equal to the displacement of fluid from thevinaster cylinder H." Attention is invited to the vfact that without changing the master cylinder parts inuany wayqthe apparatus communicating withthe master cylinder, and a l pressure responsive device in said chamber movable "by fluid entering such chamber from the master-cylinder and projecting into said motor and having mechanical connection with saidlever means for operating it. l 2. In abrake operating mechanism for a hydraulicibrake systemhaving a hydraulic brake cylinder and a pedal-controlledmaster cylinder, abooster unit comprising a high pressure cylin der communicating with the brake cylinder, a piston movable, in said high pressure cylinder to displace' fiuid therefrom, a differential pressure may be used in a braking system whereinit is desired, to displace: from the pressurewchamber 31- anamount' ofrfiuid greater than that displaced from that-master cylinder For example,many modern-trucks; etc. are provided with six wheels all of which have brake cylinders into which i fluidm-ustiqbedisplaced to effect the necessary brakingactiom ::The present apparatus, with relatively minor cha-nges involvinga, change in the proportion of ;the-parts, can be adaptedforuse with such. braking systems requiring a greater liquid displacementfrom the pressure: chamber .Th-is-maybedone either bydiecasting a v sa r rs linderf 36Iorb'y boring the cylinder element for the same], purpose, I power operated; piston unit comprisingth elements 5'8'and 59 ,w'illfbe used' with such an arrangementlandlno other pair-ts need be changed in anyway. The displacementof liquid from the pressure, chamberf 3l thus may be increasedjin proportion to the displacement from the master cylinder in acccrdancewith the brake" fluid displacement necessary fora given installation.

"It is to be understo'odthat the form of the invention herewith shown and describedis tobe taken as a preferred example" of the sameand that various changes inth'e'shape; size and arrangement orp'arts maybe resorted tovlrithohfidepartwithin "said motor casing having mechanical- A correspondingly larger 7 operated motor comprising a casing carrying said high pressure cylinder and having a pressure movable: unit therein connected to said piston; a pair of valves carriedby-said pressure movable unitan'd respectively operable for establishing differentials pressures in' said motor and for equalizing pressures therein the valve for estab lishing differentials pressures being normally closed and thelvalve' for equalizing pressures in said motor being normally open, lever means connection with both valves andoperable for first closing the pressure equalizing valve and then opening the other? valve, a low pressure cylinder carried by said motor casing in axial alinement with-said high pressure cylinder and communicating with the master cylinder, anda pressure responsive device in said low pressure cylinder movable by fluid displaced thereintoyfromthe master cylinder said pressure responsive device having mechanical; connection with said lever means to operate it and having a plunger portion projecting axially through said piston to cooperate with the latter in displacing fluid from said pressure cylinder. l l

3. Ina brake operating mechanism for a hy draulic brake system, having a hydraulic brake cylinder anda pedal-controlled master cylinder,

abooster unit comprising athigh pressure cylinmovable unit and, respectively operable for esof thesubieined claims.

1 11. arbrahe operating mechanism for a hydraulic brakesystem having a hydraulic brake cylinder and: a pedal-controlled master cylinder, aabooster unit comprising a high: pressurecylinder communicating with: the brake cylinder; a; piston pressure cylinder todisplace fluid therefrom, adifferential" fluid; pressure opclosed and the valve for tablishing diiferential pressures in said motor and for equalizing pressures therein-, the valve for establishing differential pressures being normally equalizing pressures in saidgmotor-beingnormally open; lever means withinsaid motor casing. having mechanicalconnectionwith both valvesand operable for first closingthe pressure equaliaing-l valve and: then O ening theother valve, a low pressure cylinder carried by saidg moton casing at theside thereof opposite said highpressure cylinder in axial;

alinement with the latter and communicating with the master cylinder, and a piston structure comprising a piston element mounted in said low pressure cylinder and movable by fluid entering thereinto from the master cylinder, said piston structure having a plunger portion projecting axially through the piston in said high pressure cylinder to displace fluid therefrom upon movement of said piston element, said lever means comprising a lever arranged substantially diametrically in said motor and projecting on opposite sides of the axis thereof, said piston structure being shouldered for engagement with said lever to impart movement thereto.

4. In a brake operating mechanism for a hydraulic brake system having a hydraulic brake cylinder and a pedal-controlled master cylinder, a booster unit comprising a high pressure cylinder communicatingwith the brake cylinder, a piston movable in said high pressure cylinder to displace fluid therefrom, a differential fluid pressure operated motor comprising a casing carrying said high pressure cylinder and having a pressure movable unit therein connected to said piston, a pair of valves carried by said pressure movable unit and respectively operable for establishing differential pressures in said motor and for equalizing pressures therein, the valve for establishing differential pressures being normally closed and the valve for equalizing pressures in said motor being normally open, lever means within said motor casing having mechanical connection with both valves and operable for first closing the pressure equalizing valve and then opening the other valve, a low pressure cylinder carried by said motor casing at the side thereof opposite said high pressure cylinder in axial alinement with the latter and communicating with the mastercylinder, apiston structure comprising a piston element mounted in said low pressure cylinder and movable by fluid entering thereinto from the master cylinder, said piston structure having aplunger portion-projecting axially through the piston in said high pressure cylinder to displace fluid therefrom I upon movement of said piston element, said lever means comprising a lever arranged substantially diametrically in said motor and projecting on opposite sides of the axis thereof, said piston structure being shouldered for engagement with said lever to impart move'mentthereto, and a rigid member straddling said lever and fixed to said pressure movable unit, said rigid member having lost motion connection with said piston structure-and being engageable with said low pressure cylinder to limit movement of said pressure movable unit to its position.

5. In a brake operating mechanism for a hydraulic brake system having a hydraulic brake cylinder and a pedal-controlled master cylinder, a booster unit comprising a differential fluid pressure operated motor, a high pressure cylinder and a low pressure cylinder carried by said motor and communicating respectively with the brake cylinder and with the master cylinder, said motor comprising a pressure-operable unit including a fluid displacing piston movable in said high pressure cylinder to displace fluid under pressure therefrom to the brake cylinder, followup control valve means for said motor comprising a pair of valve elements carried by and movable with said pressure-operable unit and a lever device pivoted to said pressure-operable unit and having mechanical connection with both valves to operate them, and a piston in said low pressure cylinder movable by fluid displaced into such to operate the latter.

6. In a brake operating mechanism for a hydraulic brake system having a hydraulic brake cylinder and a pedal-controlled master cylinder, a boosterunit comprising a difierentialiluid pressure operated motor having a casing and a pressure-operable unit therein including a rigid structure and a flexible diaphragm. having an inner periphery secured to said structure .and an outer periphery secured to said casing, a high pressure cylinder and a low. pressure cylinder carried by said casing and communicating respectively with the brake cylinder and with the master cylinder, a piston connected to said rigid structure and operable in said high pressure cylinder to displace fluid therefrom into the wheel cylinder, a follow-up control valve means for said motor comprising a pair of valve elements carried by and movable with said rigid structure and a lever device pivoted to said rigid structure within said casing and having mechanical connection with both valve elements for operating them, and a piston in said low pressure cylinder movable by fluid displaced into the latter from the master cylinder and having mechanical connection with said lever device to operate it.

'7. In a brake operating mechanism for a hydraulic brake system having a'hydraulic brake cylinder and a pedal-controlled master cylinder,a booster unit comprising a differential fluid' pressure operated motor having a casing and a pressure-operable unit therein dividing it into a pair of pressure chambers, a high pressure cylinder and a low pressure cylinder carried by said casing and communicating respectively with the wheel cylinder and the master cylinder, a piston connected to said-pressure operable unit and movable thereby in said high pressure cylinder, one of said pressure" chambers being in constant communication with a source of relatively low pressure, a valve carried by said pressure operable unit and normally open to connect said pressure chambers, a second valve carried by said pressure-operable unit for controlling communication between a source of higher pressure and the other pressure chamber;

a lever pivoted to said pressure operable unit and having mechanical connection with both valves, said lever being movable to close said first named valve and open said second named valve,

and apiston in said low pressure cylinder move able by fluid displaced into the latter and having mechanical connection with said lever to move it. 7

8. In a brake operating mechanism fora hydraulic-brake system having a hydraulic brake cylinder and a pedal-controlled master cylinder,

and a lever device pivoted to said pressure-operable unit and having mechanical connection with both valves to operate them, and a;piston in said low pressure cylinder movable by fluid displaced into such cylinder from thelmaster cylinder, said last named piston projecting into said motor and having mechanical connection with said lever device to operate thelatter, said last named piston and said pressure-operable unit having portions engageable independently of said lever device to limit lever-operating movement of said RUDOLPH J. KL IMKIEWI CZ.

last named piston relative to saidpressure operable unit. 

